You can call a RenderPartial and pass the model for each and enable the validation for each form independently
Main.cshml
@{ Html.RenderPartial("ChangePwd.cshtml", Model.PasswordModel); }
@{ Html.RenderPartial("MobileNo.cshtml", Model.MobileModel); }
ChangePwd.cshtml
@{Html.EnableClientValidation();}
@using (Html.BeginForm("ChangePwd", "Admin", FormMethod.Post))
{
}